It was met because your MSC is certainly having a problem as well, on top of the radio intereference.
The improvement of call drops occured only in the international cell borders, or in all the cells ?
There is no rational explanation for your problem. If the only action was to reset the MSC, and if it brought a good KPI for few days only… then your MSC is responsible. Of course, maybe someone else did something, totally unrelated to the MSC reset. You should check this..
Just for info… what’s your MSC vendor ? Maybe by knowing the brand we can find some feedback about it…